The publications and other material used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated by reference.
Generally, whole antibodies share a common Y-shape structure composed of two identical light chains and two identical heavy chains. These four polypeptide subunits are assembled so that the two heavy chains are linked, and a light chain is attached to each heavy chain by disulfide bonds. Each polypeptide constituting the antibody consists of a variable and a constant region.
The variable region is located in the arms of the Y-shaped antibody, and determines the antigen-binding specificity of the antibody. This region contains short amino acid sequences, which are responsible for the binding of the antibody to its antigen. These regions are called complementarity determining regions (CDRs). The remaining parts of the variable regions are important for the conformation of the antigen-binding pocket as a whole.
The constant region of an antibody is located at the base of the heavy chains, and determines the antibody's ability to activate immune reactions through interactions with specific receptors. These regions are generally highly conserved, and variability is limited to five basic isoforms, IgA, IgD, IgE, IgG and IgM.
Vascular adhesion protein-1 (VAP-1) is a non-classical, inflammation-inducible, adhesion molecule expressed on vascular endothelial cells, where it mediates leukocyte rolling under physiological shear. In this role it contributes towards lymphocyte re-circulation through high endothelial venules (HEV's) of secondary lymphoid tissue as part of the normal process of immune surveillance.
However, under inflammatory conditions, VAP-1 promotes the infiltration of leukocytes into inflamed tissue, thereby contributing to and maintaining the inflammatory response. This infiltration can in itself be damaging in chronic inflammatory diseases such as rheumatoid arthritis, inflammatory bowel disease, psoriasis and many autoimmune and other inflammatory diseases. In other settings, the massive infiltration of pro-inflammatory cells into tissue after the severe tissue damage resulting from myocardial infarction, stroke and other diseases contributes to the tissue destruction seen in these acute inflammatory responses. Reducing the infiltration of cells into sites of inflammation by preventing VAP-1 function with blocking antibodies is likely to allow the inflammation to resolve and lead to an improvement in the clinical symptoms of these diseases.
U.S. Pat. No. 5,580,780 describes a monoclonal antibody (mAb), 1B2, which recognizes VAP-1 and which can block lymphocyte binding to tonsillar HEV in a frozen section assay. MAb 1B2 is a murine IgM-antibody and is specific for VAP-1.
The use of murine mAbs as therapeutics has a limited potential, since the human immune system recognizes murine antibodies as foreign material and produces human anti-mouse antibodies (HAMA) to clear them from the body. This immune reaction is a major limitation to the use of murine antibodies in long-term therapy when repeated administration is needed. The use of murine anti-VAP-1 antibodies in the clinic might have to be limited to patients treated with immunosuppressants, and thus less prone to HAMA reactions, and to treatment regimens, where once only administration of the antibodies is feasible, such as in ischaemia reperfusion injury in acute infarction or acute respiratory distress syndrome.
One further disadvantage related to the use of murine IgM anti-VAP-1 antibodies in therapy is the unfavorable kinetic profile of such antibodies, i.e., the short half-life, which render them unsuitable for use in chronic disorders, such as rheumatoid arthritis, inflammatory bowel disease, psoriasis and many other diseases.
Several methods of creating less immunogenic monoclonal antibodies are known in the art. Some approaches include “humanizing” the antibodies. Frequently used strategies are to create chimeric mAbs, humanized mAbs or fully human mAbs. Chimeric mAbs are antibodies wherein the variable region is murine derived whereas the constant region is of human origin. In chimeric antibodies, approximately 70% of the rodent antibody molecule is usually replaced with the corresponding human sequences whilst maintaining the rodent antigen-binding sites with their particular specificities and affinities. Humanized antibodies are antibodies wherein the variable region may be murine derived but which has been mutated so as to more resemble a human antibody and may contain a constant region of human origin. Fully human antibodies are antibodies wherein both the variable region and the constant region are of human origin.
International patent publication WO03/093319 discloses a chimeric anti-VAP-1 monoclonal antibody BTT-1002, which has the potential to have reduced immunogenicity compared to the corresponding murine antibodies. However, being a chimeric antibody, BTT-1002 still has protein sequences corresponding to the variable regions of the antibody that are derived directly and without modification from the original mouse antibody. This antibody may still be recognized as foreign and be immunogenic when administered to man. Its pharmacological properties, such as its elimination half life and functional properties, may also be compromised due to its immunogenicity and the resulting production of antibodies against it.
Thus, there is a need in the art for a fully human anti-VAP-1 antibody with reduced immunogenicity and improved pharmacological properties.